honestly, what difference does it make what price someone got for an airline ticket? I mean, if you try an hour later, you'll get different prices most days. And depending on what airports you choose to go from/to, you can get different prices. Whatever price you see, that's what you can get AT THAT INSTANT if someone else doesn't press "I'll take it" before you do.
And as for the trip from Johannesburg to Maun, if you're actually thinking that the bus is something you have to be able to "stand", you're not going to be happy in Maun. Read a bit, Maun is not like most any city you've ever been to. Transportation in Africa - even Africa for beginners - is not like it is in Europe. There are some parts of Asia where it's similar, but for the rest of the world, it's quite unique. Even central america has "luxury" taxi's and combi's and mini-buses and buses compared to Africa. Learn to hitch-hike and ride in the back with the cow.
Don't trust the water - anywhere. And ask your doctor about Hepatitis E - it's only in Botswana.
If you still want to come, then by all means do so, and have the time of your life, and good luck finding work.